Developing a regional agricultural nonpoint salinity pollution management framework: application to the San Joaquin River, California

Irrigated agriculture in semi-arid regions typically produces drainage return flows with high salinity content. This problem requires reform to resource-management policy and the introduction of new tools to aid in sustainably addressing the issue.

This study offers a scalable decision support model for a regional water salinity management problem and accounts for political and hydrologic boundaries that produce different modes of access to water supply and drainage resources for different farms. The authors highlight the role of top-down regulations as well as market-based arrangements that might form a basis for cap-and-trade in pollution permits. They compare and discuss the various consequences of various policy interventions.

The research evaluated 64 combinations of policy interventions, consisting of fees and water use restrictions. While reductions in net revenue are observed across all policy intervention scenarios, compared with the base case scenario, none of the policy intervention scenarios led to negative net revenues, by allowing each of the subareas to fallow land, use more groundwater and shift to high-revenue crops.

As expected, the results indicate that surface water restrictions cause increases in salinity loads as more groundwater is used. The incorporation of fees for imported water is a potential policy option that can help farmers maintain lower levels of salinity loads and retain a profit. In more restrictive cases of surface water availability, results indicate that collaborative responses could provide a way for farmers to maintain revenue levels by selling and buying pollution permits.